Caption: ATP synthase enzyme complex. Illustration of the enzyme complex that drives the synthesis of the energy-carrying molecule ATP (adenosine triphosphate). Known as ATP synthase, the enzyme complex is embedded in the mitochondrial inner membrane (blue). The lower part (red) is a channel through which protons (H+) move. The upper part (yellow) is where ATP synthesis takes place. The protein complex rotates as ATP is synthesised and protons move through the channels. ATP is formed from a reaction between ADP (adenosine diphosphate) and inorganic phosphate (Pi). For this artwork with labels, see image C023/8807.